Akali's moves not doing damage

Lately there have been several times where i have had an opponent down to the last hit while playing akali. I deliver the final blow, but I do no damage. For instance, in a recent game I had jinx to one hit, I ulted on her, and she killed me. She still had the same amount of life. I did no damage. My ult should have over-killed her by a lot. The animation played. I watched akali leap into her face, but jinx took no damage. This happened to me last week against jax too, and he wasn't doing his damage block thing either. I really think there is a problem and you should look into why akali's ult just doesn't do any damage sometimes.